Electronic assemblies used in two-way radios and other electronic devices which emit or are used in the vicinity of radio frequency and electromagnetic radiation, sometimes require shielding from electromagnetic and radio frequency interference (EMI and RFI). One such assembly is the radio frequency power amplifier module used in two-way radios. Present radio frequency power amplifier modules are typically manufactured by attaching the power amplifier substrate carrying the power amplifier electronics (e.g., power amplifier, etc.) onto a heat sink used to dissipate heat away from the amplifier using known attachment techniques, such as by soldering the substrate onto the heat sink or by using conductive adhesives. After the power amplifier substrate is attached to the heat sink, a metal shield is then attached to the heat sink using epoxy or other conductive adhesives which are applied to the joints between the shield and heat sink and then allowed to cure in an oven. The shield providing for an EMI/RFI protection to the power amplifier electronics.
One major problem of attaching the shield to the heat sink using the prior art method of epoxy application is that the process takes too much time. A typical shield attachment step using epoxy takes in the order of one and a half hours. Other problems associated with the use of epoxy to attach the shield to the module are problems with the conductive epoxy "running" into the power amplifier substrate during the time the epoxy is curing and causing electrical shorts to occur in the power amplifier circuit. Also, the epoxy while curing sometimes lifts the shield away from the power amplifier module due to a mismatch in the coefficient of expansion, causing a decrease in the amount of RFI/EMI attenuation provided by the shield. Finally, since conductive adhesives have to be cured under controlled conditions, a faulty adhesive curing process can cause the adhesive to fail and the shield to fall off the power amplifier module. A need thus exists in the art for a method for attaching a metallized shield onto an electronic assembly which can overcome the noted problems.